At my university in Canada we have a lot of Mandarin-speaking students and Mandarin-speaking exchange students, as well as students who speak Cantonese. My aunt, uncle, and cousins who are half-Chinese speak Cantonese and don’t understand Mandarin (my family is Vietnamese).
I’m just wondering if there are a lot of Mandarin speakers who can also speak Cantonese well? When I go to some Chinese restaurants some of the waiters know both languages (they probably make sure to hire these waiters because of that) I know that both dialect speakers can communicate to each other by writing, because the writing system is similar.